The present claimed invention relates to the field of semiconductor processing. More specifically, the present claimed invention relates to the removal of post etch residues during semiconductor processing.
The geometries of semiconductor devices are aggressively being scaled smaller and smaller to meet cost reduction and real estate requirements. Consequently, more polymers are needed during etch processes to protect exposed sidewalls and underlying layers while maintaining tight profile control and better etch selectively. As a result of the use of the additional polymers, complete and thorough polymer removal is becoming increasingly challenging.
Also, semiconductor fabrication processes are also now incorporating various new materials including: new multiple dielectrics, metals, and resists, to achieve better device performance. The recently incorporated new materials have also necessitated the development of new etch processes. Some of the new etch sources for etching the new materials have complex etch chemistries which, in turn, create new etch residues. Traditionally, wet or dry clean processes, or their combinations, are used to ensure etch residue removal and to achieve the required low-contact resistance in, for example, vias. Experiments have shown, however, that conventional wet or dry clean processes cannot effectively remove the etch residues especially in high respect ratio etch environments such as, for example, via etching. Attempts have also been made to introduce fluorine-based chemicals within a low temperature cleaning process, but such fluorine-based chemicals deleteriously damage oxide-based dielectric materials. Also, conventional wet clean process steps typically require the use of a solvent that can be toxic, costly to use and dispose of, and which is difficult to handle. Moreover, in many cases, the chemical reactions occurring during the wet clean processes do. not produce enough activation energy to remove all of the etch residues. As a result, deleterious post etch residues remain, for example, in vias of the semiconductor devices being formed. Post etch residues which remain in contact holes, vias, or various other structures of the semiconductor device may ultimately result in device failure.
In yet another conventional approach, a dry clean process is employed in an attempt to remove post etch residues. Conventional dry cleaning approaches are based on a plasma process. The traditional plasma excitation source used in a dry clean process can damage the semiconductor device due to the relatively large number of high-energy ions present in the plasma region. These high-energy ions can sputter chamber walls, create dielectric damage, and form unwanted driven-in mobile ions within the semiconductor wafer. Hence, traditional plasma-based dry clean processes have corresponding disadvantages which render them poorly suited to the removal of post etch residues.
In still another conventional approach, microwave downstream plasma processing has been employed to remove post etch residues. The microwave downstream plasma process offers low damage performance. Unfortunately, however, the microwave downstream plasma process requires that the semiconductor wafers be heated to quite high temperatures. Specifically, in order to achieve a reasonable throughput, conventional microwave downstream plasma processes require heating the semiconductor wafer to temperatures in the range of 200 degrees Celsius or higher. The use of such high temperatures can cause post etch polymer residues to harden on the wafer, thereby rendering their removal even more difficult.
As yet another concern, in order to achieve widespread acceptance, and to ensure affordability, any method of removing post etch residues, which overcomes the above-listed drawbacks, should be compatible with existing semiconductor fabrication processes.
Thus, the need has arisen for a method and system to remove post etch residues. Another need exists for a method and system which meet the above needs and which does not suffer from the disadvantages associated with conventional post etch residue removal approaches. Yet another need exists for a method and system for removing post etch residues which meet the above needs and which are compatible with existing semiconductor fabrication processes such that significant revamping of semiconductor capital equipment is not required.
The present invention provides a method and system to remove post etch residues. The present invention further provides a method and system which achieve the above accomplishments and which does not suffer from the disadvantages associated with conventional post etch residue removal approaches. The present invention also provides a method and system for removing post etch residues which achieve the above accomplishments and which are compatible with existing semiconductor fabrication processes such that significant revamping of semiconductor capital equipment is not required.
Specifically, in one method embodiment the present invention recites disposing a surface, having post etch residues adhered thereto, proximate to an electron beam source which generates electrons. The present method embodiment then recites bombarding the post etch residues with the electrons such that the post etch residues are removed from the surface to which the post etch residues were adhered.
In another embodiment, the present invention includes the steps of the above-described embodiment and further recites transporting the loosened post etch residues away from the surface, to which the post etch residues were adhered, by creating a vacuum proximate the surface.